This application is connected with U.S. patent applications Ser. Nos. 07/795,989 (filed Nov. 2, 1991), 07/850,283 (filed Mar. 12, 1992), 07/878,469 (filed May 5, 1992), 07/939,600 (filed Sep. 2, 1992) and 07/969,072 (filed Oct. 30, 1992).
1. Field of the Invention
The present invention relates in general to automotive automatic transmissions, and more particularly to a control system for the automotive automatic transmissions.
2. Description of the Prior Art
In order to clarify the task of the present invention, one conventional control system for automotive automatic transmissions will be outlined, which is shown in Japanese Patent First Provisional Publication 1-188750.
In this conventional control system, there is employed a measure by which in carrying out a specified gear change, the actual switching of associated solenoids is carried out when the rotation speed ratio between the input and output shafts of the transmission comes to a predetermined value. That is, the actual switching of the solenoids is not strictly timed with the time when necessity of the gear change is judged. With the measure, appropriate gear change timing is obtained even in a so-called "jump over gear change" wherein the gear change is carried out skippingly and a so-called "foot release gear change" wherein the gear change is carried out with a driver's foot kept released from the accelerator pedal.
However, in the above-mentioned conventional control system, the specified gear change is always made by putting a certain one-way clutch to OFF condition from ON condition. That is, gear changes other than the specified gear change are made by having the one-way clutch kept in ON condition. However, in this case, the following undesirable phenomenon tends to occur. That is, in the gear changes other than the specified gear change, the rotation speed ratio between the input and output shafts of the transmission fails to obtain the predetermined value. This means that such gear changes never take place.